The provision of an organic layer which is bonded to the surface of a substrate having insulating, metallic, conductive, or electronic properties is essential in building up devices for use as an interface between inorganic materials and organic or biological materials. Examples of interfaces using a biological/inorganic material interface are materials for in vivo implant, for example, bone ingrowth-promoting orthopedic implants and implantable biosensors that utilize a bioactive layer to detect a chemical or biological species. In such biosensor devices, a biologically active layer (also referred to herein as an bioactive layer) is coupled to a semi-conductor layer to generate an electronic or optical signal proportional to the amount or concentration of the species detected. Devices utilizing an organic/inorganic material interface are, for example, organic-based transistors (OT's) and light emitting diodes (OLED's).
The mechanical, chemical, and electronic properties of the interface between an organic or bioactive layer and an inorganic substrate depend upon many factors, not the least of which are: (a) the organization of the molecular moieties comprising the layer, for example, their alignment and attachment to the substrate's surface; and (b) the area specific density of bonds between the surface of the substrate and the organic layer. Additionally, the interface must display chemically stability and be robust under the conditions of use or it will deteriorate in use.
As described in copending U.S. application Ser. No. 10/701,591, filed Nov. 4, 2003, Ser. No. 10/405,557, filed Apr. 1, 2003, and Ser. No. 10/179,743, filed Jun. 24, 2002, each of which is incorporated herein by reference in their entirety, and as described in U.S. Pat. No. 6,433,359 to Kelley et al., it is known that a phosphorous acid can be used to provide a layer which adheres to an oxide surface. In general, the approach to providing layers utilizing acids of this type has been to treat the surface directly by spinning on, painting on or immersing (also termed herein “dip coating”) a coating composition comprising the acid. These methods typically provide poorly organized coatings, or require equipment and techniques which do not readily lend themselves to substrates which are larger than a disc or which require that the coating be applied in a pattern.
Accordingly, the inventors have recognized the need for the provision of coatings which have an improved degree of organization and/or improved adhesion strength and/or which can be applied to surfaces over a large area, particularly when the coating is to be applied in a pattern.